free cooling

What is free cooling?

Free cooling is an approach to lowering the air temperature in a building or data center by using naturally cool air or water instead of mechanical refrigeration. In practice, free cooling is not entirely free because pumps, fans, and other air and water-handling equipment is needed. That equipment also requires periodic maintenance and repairs.

The prevailing air at many latitudes and elevations can be considerably cooler during certain seasons and times of day than the air warmed by data center equipment. By filtering, humidifying and introducing cooler prevailing air directly into the data center, it is possible to reduce or eliminate the use of industrial-grade computer room air conditioning systems. Cooling systems that use this approach are sometimes called airside economizers.

Alternatively, a source of cold water from local rivers, lakes or ocean sources can circulate into a data center instead of undergoing the traditional method of refrigerating a closed water loop with a chiller. Systems that use this approach are often called waterside economizers, which can either be used to cool room air or directly cool cabinets and other systems.

In both cases, the industrial cooling systems are necessary when the outside air temperatures become too high for free cooling systems, like air- or water-side economizers, to be effective. Consequently, the working life of installed cooling systems can be significantly extended.

Limiting cooling system use leads to reductions in data center power consumption, services and repairs. This practice lowers the energy and maintenance costs for facility owners as well as introduces a greener environment for data center operations.

This was last updated in April 2024

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